1. Field of the Invention
The present invention relates to a Group III nitride-based compound semiconductor light-emitting device, and more particularly, to a Group III nitride-based compound semiconductor light-emitting device conductive in which a p-layer is joined to a conductive support substrate via a layer made of conductive material, and an n-layer is disposed on a light extraction side.
The present invention is applicable to a light-emitting device produced through a so-called laser lift-off technique; i.e., a light-emitting device produced through epitaxially growing, on a hetero-substrate, a Group III nitride-based compound semiconductor, to thereby form a light-emitting device structure; bonding a conductive support substrate to the structure via a conductive layer made of metal, solder, or the like; and separating the hetero-substrate by irradiating, with laser light, the Group III nitride-based compound semiconductor thin layer present in the vicinity of the interface between the semiconductor and the hetero-substrate. The Group III nitride-based compound semiconductor light-emitting device of the present invention has an n-layer and a p-layer sandwiching pn junction or an active layer.
2. Background Art
The present inventors previously disclosed, in Japanese Patent Application Laid-Open (kokai) No. 2007-158128, a method for producing Group III nitride-based compound semiconductor light-emitting device through a so-called laser lift-off technique. A general feature of the disclosed Group III nitride-based compound semiconductor light-emitting device resides in that a p-layer is joined to a conductive support substrate via a layer made of conductive material, and an n-layer is disposed on the light extraction side. Generally, the electrode to be formed on the light extraction side (n-layer side) is not a transparent electrode but is formed from a metal or alloy providing ohmic contact. In the device, since the n-contact electrode formed on the n-layer impedes light extraction, the electrode must be formed into, for example, a line shape, and current is supplied to the entirety of the light-emitting area as uniformly as possible.
In a Group III nitride-based compound semiconductor light-emitting device produced through a laser lift-off process and having an n-layer side serving as a light extraction side, a large contact area between a p-layer and a p-contact electrode can be realized, and the material of the p-contact electrode can be selected mainly from the viewpoints of reflection characteristics and contact resistance. Therefore, as compared with Group III nitride-based compound semiconductor light-emitting devices of other structures, the light-emitting device produced through a laser lift-off process is useful for a large-scale (e.g., 1 mm×1 mm) planar device operating with large current. However, since the n-contact electrode formed on the light extraction side impedes light extraction, the design of the n-contact electrode leaves room for further improvement.